Figure 6.

Variation in the human electroencephalogram (EEG) spectra during daytime and nighttime monochromatic light exposure. Log-transformed averaged EEG power density during 6.5 h monochromatic light exposure (460 nm and 555 nm, equal photon density of 2.8 × 10¹³ photons/cm²/s) was expressed relative to EEG power density during the same clock time 48 h earlier (dim light < 3 lux) under constant routine (100%, dotted line). Average EEG power density in each 0.5 Hz frequency bin was compared between 460 nm and 555 nm exposure during daytime (A) and nighttime (B). Comparisons between daytime and nighttime for the 460 nm (C) and 555 nm (D) exposures are also shown. Differences between blue and green monochromatic lights (panels A,B), and between daytime and nighttime (panels C,D) are denoted by * (p < 0.05). Figure and legend adapted from [11,55].